Final answer:
The nipple sensation is served by the T4 dermatome, which is tested during a sensory exam using light touch to assess sensory integrity.
Step-by-step explanation:
The sensation of the nipple area is primarily served by the T4 (fourth thoracic) dermatome. Dermatomes are areas of skin that are innervated by sensory fibers from a single spinal nerve root. During a sensory exam, the integrity of these dermatomes can be assessed to ensure that the sensory pathways are functioning properly. This is often done by using a simple stimulus, like a cotton-tipped applicator, to apply a light touch to the skin in various dermatomes, including around the nipple area, to check for any sensory loss or difference in perception. Spinal nerves are responsible for transmitting this sensory information from the dermatomes to the brain, where it is perceived.